This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A189564 #11 Mar 19 2017 16:01:41 %S A189564 1,1,2,6,24,120,336,1474,8340,57756,475658,4171070,41950294,472535256, %T A189564 5882635676,79963449714,1173614446044 %N A189564 Number of permutations p of 1,2,...,n satisfying |p(i+1)-p(i)|<>5 and |p(j+5)-p(j)|<>1 for all i=1..n-1, j=1..n-5. %C A189564 a(n) is also the number of ways to place n nonattacking pieces rook + leaper[1,5] on an n X n chessboard. %H A189564 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Number of ways of placing non-attacking queens, kings, bishops and knights</a> (in English and Czech) %F A189564 Asymptotic: a(n)/n! ~ 1/e^4. %Y A189564 Cf. A137774, A189358, A189563. %K A189564 nonn,more,hard %O A189564 0,3 %A A189564 _Vaclav Kotesovec_, Apr 23 2011